The cold weather we have had has put the bees into tighter clusters. With the contracting of the cluster of bees, there will probably be some brood mortality in some colonies. The earlier warm weather, let the bees expand their brood areas. Now with the colder weather, the bees may not be able to cover all the brood that the queen had laid. This uncovered brood will more than likely get chilled and die. Don't be surprised if you start seeing dead brood and or bees in front of the hive when the temperatures warm up. This will set the hive back a little but it won't hurt them in the long term.
Walk away splits should not be done in this cooler weather. The cool weather may chill the brood that the covering bees have been shaken off of. A large number of brood could perish during the time it takes for the bees to reoccupy the split that has no bees covering and protecting the brood. Stick with a traditional split and there will be no problems.